The cleaning of dusty air still presents many problems, despite the many proposals in the art for its accomplishment. Where conventional filtration is employed the filters load up with dust, and elaborate provision needs to be made for cleaning the filters, resulting in the need for over-capacity to provide for shutting down of individual filter units during the cleaning process, while maintaining the apparatus in operation. Cyclone dust collectors are bulky, and tend to discharge a substantial amount of dust in the fine size ranges--requiring a substantial final filtering operation to produce an acceptably clean air discharge. Wet scrubbers present the problem of sludge disposal--usually in ponds. Electrostatic precipitators present other problems, including the need for handling of the high voltages involved. To date, the provision of an economical means of cleaning dusty air, involving minimal floor space and minimal mechanical and electrical complication, has remained an elusive goal in the art.